1. Field of the Invention
The present invention relates to an opposite layout substrate alignment method and device and a liquid crystal display and particularly to an opposite layout substrate alignment method and device just suitable for manufacture of a TFT system liquid crystal display and an LCD manufactured using the same method.
2. Description of the Related Art
In a well known liquid crystal display (LCD) apparatus, characters and images are displayed by transmitting and reflecting the light beam through changes of molecular alignment generated when a voltage is applied across the liquid crystal filled between two glass plates. As a kind of such liquid crystal display, there is proposed a liquid crystal display of a thin film transistor (TFT) system. This TFT system liquid crystal display is preferable in the viewpoints of contrast, gradation display and response rate because each pixel of a display area is controlled by a thin film transistor, and thereby display flicker is reduced.
Here, a method of manufacturing existing liquid crystal display and an apparatus manufactured will be explained with reference to the drawings. FIG. 4 illustrates a process flow of manufacturing an LCD, FIG. 5 illustrates a detail flow of an alignment process in the process flow of FIG. 4, and FIGS. 6A and 6B illustrate stages of an existing aligning apparatus. FIG. 6A is a plan view, while FIG. 6B is a cross-sectional view. FIG. 7 is a cross-sectional view illustrating when a substrate is set in the existing stage. FIGS. 8A and 8B illustrate alignment in the existing stages. FIG. 8A is a cross-sectional view and FIG. 8B is an enlarged view.
As illustrated in FIG. 4, in the process flow of manufacturing an LCD, cleaning, coating of alignment film, rubbing (single alignment process of molecule), cleaning, spraying of spacer (transparent glass, resin or the like) are previously performed to the TFT substrate. Moreover, cleaning, coating of alignment film, rubbing, cleaning, coating of sealing agent are previously performed to an opposite layout substrate. The TFT substrate and opposite layout substrate having completed the above processes are aligned and liquid crystal is then supplied to the space between these substrates.
Details of such alignment process are as follows. First, the TFT substrate on which spacer is coated and an opposite layout substrate on which a sealing agent consisting, for example, of UV hardening type epoxy resin are prepared (step S50). Next, temporary alignment of the TFT substrate and opposite layout substrate is once performed (step S51) and thereafter the alignment operation (positioning of TFT pixels and RGB pixels) is performed (step S52) by respectively moving the substrates under the temporary aligned condition in the directions of X, Y and xcex8 within the range of the predetermined allowance. Thereafter, the press work is then conducted to press the sealing agent up to the predetermined gap (step S53) and the sealing agent is then hardened through the heat treatment or UV radiation (step S54). Thereby the alignment process is completed.
For performing the alignment shown in the step S52, a stage 100 of the alignment apparatus illustrated in FIGS. 6A and 6B is used. In the stage 100, the groove 101a for vacuum-holding a substrate is formed in the shape of a letter H at the upper surface of a flat block 101, a vacuum-holding hole 101b is bored toward the bottom surface from the center of the letter H, and this vacuum-holding hole 101b is bent in the horizontal direction and is then connected to a vacuum pipe not illustrated.
On this stage 100, when a substrate 110 is placed as illustrated in FIG. 7, the substrate 110 becomes flat depending on the surface of stage.
Therefore, at the time of starting the alignment operation, the temporarily aligned LCD 150 is held between the stage 120 in the TFT substrate side and the stage 130 in the opposite layout substrate side as illustrated in FIGS. 8A and 8B. Under this condition, the TFT substrate 15 and opposite layout substrate 152 are respectively fixed to the stages 120, 130 by the vacuum sticking. When the alignment operation is performed in the X, Y and xcex8 directions in such fixing condition, the alignment film coated on the substrate surfaces may be sometimes damaged by the spacer 161. Numeral 162 designates the sealing agent.
When the TFT system liquid crystal display, for example, is manufactured using the manufacturing apparatus of the related art explained above, there arise the following problems.
{circle around (1)} As display density of display area is further improved, size of one TFT pixel is further reduced and thereby a fault in size which has been neglected in the related art will be considered as a serious matter.
{circle around (2)} As explained above, spacer is sprayed to keep uniform gap between both TFT substrate and opposite layout substrate, this spacer will damage the alignment film at the time of alignment operation and such damage will progress as a fault in some cases. In view of avoiding damage of alignment film due to this spacer, following methods have been introduced. Namely, the spacer having a grain size larger than that of the spacer for gap control is mixed to the sealing area in order to prevent damage during the alignment and the press work is performed until the normal gap can be attained after the end of alignment.
However, in the means for avoiding damage on the alignment film by the related art, two kinds of spacers having small and large grain sizes are required. Moreover, the process for previously mixing the spacer having larger gain size into the sealing agent has been required.
It is therefore an object of the present invention to provide an opposite layout substrate alignment method and device which surely prevents damage on the inside of a substrate (alignment film) even when the spacer provided between the substrate has only one kind of grain size and an LCD manufactured by the same method.
In order to attain the object explained above, the present invention proposes an alignment method of the opposite layout substrate to realize alignment between two substrates provided opposed with each other, which is characterized in that alignment is performed under the condition that the recessed area is formed at least to one opposing surface of the two substrates.
Moreover, the present invention proposes an alignment device for the opposite layout substrate to perform alignment between two substrates provided opposed with each other, which is characterized by comprising a recessed area forming means to form a recessed area at least to one opposing surface of the two substrates.
In addition, the present invention proposes an LCD consisting of the TFT substrate in which many TFTs are integrated through formation and an opposite layout substrate aligned to such TFT substrate keeping the predetermined gap, which is characterized in that these substrates are aligned under the condition that a recessed area is formed at least to one opposing surface of two substrates.
Thereby, as illustrated in FIG. 3, for example, particles (spacer) arranged between the substrates will never damage the internal surfaces of the substrate even when alignment is performed, because a space may be formed due to formation of the recessed area between two substrates.